Linear regulators and in particular low drop out linear voltage regulators (LDOs) can be used to provide a regulated voltage. As such, linear regulators are important building blocks of many power management systems.
Within its operating range, a linear regulator provides a constant output DC voltage regardless of the input voltage or load current. This is achieved by sensing the output voltage and regulating a current source. The output voltage is regulated using a feedback loop which is stabilised using a compensation circuit. After a change in load current, the linear regulator requires a certain amount of time, also referred to as transient response time, to return to steady state conditions. Existing LDO circuits which implement a frequency compensation technique, require the use of a large compensation capacitor. This increases the size of the circuit and slows down the transient response of the regulator.
Compensations techniques based on current amplifiers have also been proposed. In this scenario a compensation capacitor is amplified through a current amplifier integrated into the regulation loop. However, these circuits have a limited multiplication factor and suffer from instability.